vega_templates: Handle content as dict instead of string. (#124)

Prevent unnecessary `dumps`/`loads` calls.

Closes #23

src/dvc_render/vega.py

@@ -1,16 +1,11 @@
-from copy import deepcopy
+import json
 from pathlib import Path
-from typing import List, Optional
+from typing import Any, Dict, List, Optional
 from warnings import warn
 
 from .base import Renderer
-from .exceptions import DvcRenderException
 from .utils import list_dict_to_dict_list
-from .vega_templates import LinearTemplate, get_template
-
-
-class BadTemplateError(DvcRenderException):
-    pass
+from .vega_templates import BadTemplateError, LinearTemplate, get_template
 
 
 class VegaRenderer(Renderer):
@@ -44,16 +39,15 @@ def __init__(self, datapoints: List, name: str, **properties):
 
     def get_filled_template(
         self, skip_anchors: Optional[List[str]] = None, strict: bool = True
-    ) -> str:
+    ) -> Dict[str, Any]:
         """Returns a functional vega specification"""
+        self.template.reset()
         if not self.datapoints:
-            return ""
+            return {}
 
         if skip_anchors is None:
             skip_anchors = []
 
-        content = deepcopy(self.template.content)
-
         if strict:
             if self.properties.get("x"):
                 self.template.check_field_exists(
@@ -76,20 +70,20 @@ def get_filled_template(
             if value is None:
                 continue
             if name == "data":
-                if self.template.anchor_str(name) not in self.template.content:
+                if not self.template.has_anchor(name):
                     anchor = self.template.anchor(name)
                     raise BadTemplateError(
                         f"Template '{self.template.name}' "
                         f"is not using '{anchor}' anchor"
                     )
             elif name in {"x", "y"}:
                 value = self.template.escape_special_characters(value)
-            content = self.template.fill_anchor(content, name, value)
+            self.template.fill_anchor(name, value)
 
-        return content
+        return self.template.content
 
     def partial_html(self, **kwargs) -> str:
-        return self.get_filled_template()
+        return json.dumps(self.get_filled_template())
 
     def generate_markdown(self, report_path=None) -> str:
         if not isinstance(self.template, LinearTemplate):

src/dvc_render/vega_templates.py

@@ -1,3 +1,4 @@
+# pylint: disable=missing-function-docstring
 import json
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, Dict, List, Optional, Union
@@ -27,67 +28,102 @@ def __init__(self, template_name: str, path: str):
         )
 
 
+class BadTemplateError(DvcRenderException):
+    pass
+
+
+def dict_replace_value(d: dict, name: str, value: Any) -> dict:
+    x = {}
+    for k, v in d.items():
+        if isinstance(v, dict):
+            v = dict_replace_value(v, name, value)
+        elif isinstance(v, list):
+            v = list_replace_value(v, name, value)
+        elif isinstance(v, str):
+            if v == name:
+                x[k] = value
+                continue
+        x[k] = v
+    return x
+
+
+def list_replace_value(l: list, name: str, value: str) -> list:  # noqa: E741
+    x = []
+    for e in l:
+        if isinstance(e, list):
+            e = list_replace_value(e, name, value)
+        elif isinstance(e, dict):
+            e = dict_replace_value(e, name, value)
+        elif isinstance(e, str):
+            if e == name:
+                e = value
+        x.append(e)
+    return x
+
+
+def dict_find_value(d: dict, value: str) -> bool:
+    for v in d.values():
+        if isinstance(v, dict):
+            return dict_find_value(v, value)
+        if isinstance(v, str):
+            if v == value:
+                return True
+    return False
+
+
 class Template:
-    INDENT = 4
-    SEPARATORS = (",", ": ")
     EXTENSION = ".json"
     ANCHOR = "<DVC_METRIC_{}>"
 
-    DEFAULT_CONTENT: Optional[Dict[str, Any]] = None
-    DEFAULT_NAME: Optional[str] = None
-
-    def __init__(self, content=None, name=None):
-        if content:
-            self.content = content
-        else:
-            self.content = (
-                json.dumps(
-                    self.DEFAULT_CONTENT,
-                    indent=self.INDENT,
-                    separators=self.SEPARATORS,
-                )
-                + "\n"
-            )
-
+    DEFAULT_CONTENT: Dict[str, Any] = {}
+    DEFAULT_NAME: str = ""
+
+    def __init__(
+        self, content: Optional[Dict[str, Any]] = None, name: Optional[str] = None
+    ):
+        if (
+            content
+            and not isinstance(content, dict)
+            or self.DEFAULT_CONTENT
+            and not isinstance(self.DEFAULT_CONTENT, dict)
+        ):
+            raise BadTemplateError()
+        self._original_content = content or self.DEFAULT_CONTENT
+        self.content: Dict[str, Any] = self._original_content
         self.name = name or self.DEFAULT_NAME
-        assert self.content and self.name
         self.filename = Path(self.name).with_suffix(self.EXTENSION)
 
     @classmethod
     def anchor(cls, name):
         "Get ANCHOR formatted with name."
         return cls.ANCHOR.format(name.upper())
 
-    def has_anchor(self, name) -> bool:
-        "Check if ANCHOR formatted with name is in content."
-        return self.anchor_str(name) in self.content
-
-    @classmethod
-    def fill_anchor(cls, content, name, value) -> str:
-        "Replace anchor `name` with `value` in content."
-        value_str = json.dumps(
-            value, indent=cls.INDENT, separators=cls.SEPARATORS, sort_keys=True
-        )
-        return content.replace(cls.anchor_str(name), value_str)
-
     @classmethod
     def escape_special_characters(cls, value: str) -> str:
         "Escape special characters in `value`"
         for character in (".", "[", "]"):
             value = value.replace(character, "\\" + character)
         return value
 
-    @classmethod
-    def anchor_str(cls, name) -> str:
-        "Get string wrapping ANCHOR formatted with name."
-        return f'"{cls.anchor(name)}"'
-
     @staticmethod
     def check_field_exists(data, field):
         "Raise NoFieldInDataError if `field` not in `data`."
         if not any(field in row for row in data):
             raise NoFieldInDataError(field)
 
+    def reset(self):
+        """Reset self.content to its original state."""
+        self.content = self._original_content
+
+    def has_anchor(self, name) -> bool:
+        "Check if ANCHOR formatted with name is in content."
+        found = dict_find_value(self.content, self.anchor(name))
+        return found
+
+    def fill_anchor(self, name, value) -> None:
+        "Replace anchor `name` with `value` in content."
+        self.content = dict_replace_value(self.content, self.anchor(name), value)
+
 
 class BarHorizontalSortedTemplate(Template):
     DEFAULT_NAME = "bar_horizontal_sorted"
@@ -606,7 +642,7 @@ def get_template(
     _open = open if fs is None else fs.open
     if template_path:
         with _open(template_path, encoding="utf-8") as f:
-            content = f.read()
+            content = json.load(f)
         return Template(content, name=template)
 
     for template_cls in TEMPLATES:
@@ -635,6 +671,6 @@ def dump_templates(output: "StrPath", targets: Optional[List] = None) -> None:
         if path.exists():
             content = path.read_text(encoding="utf-8")
             if content != template.content:
-                raise TemplateContentDoesNotMatch(template.DEFAULT_NAME or "", path)
+                raise TemplateContentDoesNotMatch(template.DEFAULT_NAME, str(path))
         else:
-            path.write_text(template.content, encoding="utf-8")
+            path.write_text(json.dumps(template.content), encoding="utf-8")

tests/test_templates.py

@@ -1,3 +1,4 @@
+import json
 import os
 
 import pytest
@@ -38,8 +39,9 @@ def test_raise_on_no_template():
     ],
 )
 def test_get_template_from_dir(tmp_dir, template_path, target_name):
-    tmp_dir.gen(template_path, "template_content")
-    assert get_template(target_name, ".dvc/plots").content == "template_content"
+    template_content = {"template_content": "foo"}
+    tmp_dir.gen(template_path, json.dumps(template_content))
+    assert get_template(target_name, ".dvc/plots").content == template_content
 
 
 def test_get_template_exact_match(tmp_dir):
@@ -51,13 +53,16 @@ def test_get_template_exact_match(tmp_dir):
 
 
 def test_get_template_from_file(tmp_dir):
-    tmp_dir.gen("foo/bar.json", "template_content")
-    assert get_template("foo/bar.json").content == "template_content"
+    template_content = {"template_content": "foo"}
+    tmp_dir.gen("foo/bar.json", json.dumps(template_content))
+    assert get_template("foo/bar.json").content == template_content
 
 
 def test_get_template_fs(tmp_dir, mocker):
-    tmp_dir.gen("foo/bar.json", "template_content")
+    template_content = {"template_content": "foo"}
+    tmp_dir.gen("foo/bar.json", json.dumps(template_content))
     fs = mocker.MagicMock()
+    mocker.patch("json.load", return_value={})
     get_template("foo/bar.json", fs=fs)
     fs.open.assert_called()
     fs.exists.assert_called()

tests/test_vega.py

@@ -1,5 +1,3 @@
-import json
-
 import pytest
 
 from dvc_render.vega import BadTemplateError, VegaRenderer
@@ -33,7 +31,6 @@ def test_init_empty():
     assert renderer.name == ""
     assert renderer.properties == {}
 
-    assert renderer.generate_html() == ""
     assert renderer.generate_markdown("foo") == ""
 
 
@@ -43,7 +40,7 @@ def test_default_template_mark():
         {"first_val": 200, "second_val": 300, "val": 3},
     ]
 
-    plot_content = json.loads(VegaRenderer(datapoints, "foo").partial_html())
+    plot_content = VegaRenderer(datapoints, "foo").get_filled_template()
 
     assert plot_content["layer"][0]["mark"] == "line"
 
@@ -60,7 +57,7 @@ def test_choose_axes():
         {"first_val": 200, "second_val": 300, "val": 3},
     ]
 
-    plot_content = json.loads(VegaRenderer(datapoints, "foo", **props).partial_html())
+    plot_content = VegaRenderer(datapoints, "foo", **props).get_filled_template()
 
     assert plot_content["data"]["values"] == [
         {
@@ -85,7 +82,7 @@ def test_confusion():
     ]
     props = {"template": "confusion", "x": "predicted", "y": "actual"}
 
-    plot_content = json.loads(VegaRenderer(datapoints, "foo", **props).partial_html())
+    plot_content = VegaRenderer(datapoints, "foo", **props).get_filled_template()
 
     assert plot_content["data"]["values"] == [
         {"predicted": "B", "actual": "A"},
@@ -100,12 +97,8 @@ def test_confusion():
 
 
 def test_bad_template():
-    datapoints = [{"val": 2}, {"val": 3}]
-    props = {"template": Template("name", "content")}
-    renderer = VegaRenderer(datapoints, "foo", **props)
     with pytest.raises(BadTemplateError):
-        renderer.get_filled_template()
-    renderer.get_filled_template(skip_anchors=["data"])
+        Template("name", "content")
 
 
 def test_raise_on_wrong_field():
@@ -177,7 +170,7 @@ def test_escape_special_characters():
     ]
     props = {"template": "simple", "x": "foo.bar[0]", "y": "foo.bar[1]"}
     renderer = VegaRenderer(datapoints, "foo", **props)
-    filled = json.loads(renderer.get_filled_template())
+    filled = renderer.get_filled_template()
     # data is not escaped
     assert filled["data"]["values"][0] == datapoints[0]
     # field and title yes